The BBC's websites (e.g. news.bbc.co.uk and www.bbc.co.uk) are either down or very slow to respond from multiple ISPs and countries. It feels like a DDOS attack, but I cannot confirm it.
It's not trending on Twitter yet, but you can see that it's a widespread issue in real time. The BBC was subject to a major DDOS attack almost exactly a year ago.
Update: the BBC have a statement blaming "network problems" here. Perhaps they should be blaming Siemens?